In recent years the hydraulic excavator and loader-backhoe have become increasingly popular as a means of moving material in and around construction sites and just as the excavator and loader-backhoe population has increased so has the variety of attachments for these machines. Thus, in order to utilize his equipment to the fullest, it is not uncommon for the owner of such equipment to have several attachments such as a trenching or digging bucket, a ditching or finishing bucket or a hydraulic rock hammer, drill or tamper.
Conventionally, the changing from one attachment to another requires the driving or pressing out of pins which were used to mount these attachments to the arm of these machines. Over a period of years there have been several types of quick-coupling devices designed and patented. Some of these couplings utilize a form of an adapter which pins to the arm of the excavator and contains either a female or male receptacle which engages a corresponding male or female receptacle on the attachment, an example of which is disclosed in Canadian Patent No. 1,081,171. The problem which arises from this type of coupler is that it moves the pivot point of the bucket further from the cutting edge of the bucket or tip radius, which greatly reduces the digging force of the bucket. Also because of the extra weight of the adapter and associated receptacles in comparison to a standard bucket, the lifting capacity of the excavator is affected in that the capacity of the bucket will be reduced in relationship to the extra weight of the adapter and therefore the performance is affected.
Other designs have been developed to overcome the adapter problem. One such type is Canadian Patent No. 1,109,427 which uses links between the pivot pin and power link pin. These links and protruding pins and sleeves are designed to engage hinge plates or mounting lugs which are attached to the bucket or attachment and to the rear with a spring loaded locking arrangement. The positioning of the receptacles in the hinge plates is very close to the original pin bores so as not to affect the digging geometry and forces. But by having the receptacle in the hinge plate which receives the pivot pin in the arm open towards the front or cutting edge of the bucket, when the arm is pulled in toward the machine, as in the digging cycle, all the force generated at the pivot pin is now transferred to the rear or power link pin which differs from an original bucket.
With the increasing use of hydraulic rock hammers on demolition and excavating sites because of the restrictive use of explosives, another problem with quick couplers has surfaced. The problem is that a hydraulic hammer mounted on the arm of an excavator produces very severe reciprocating movement on the mounting pins and coupling and this has a tendency to loosen the coupling arrangement on many quick couplers currently available for excavators and loader backhoes. As can be seen in Canadian Patents 1,109,427 and 1,259,958 there is no provision to positively lock the front pin in the coupling arrangement. This movement causes accelerated wear on the parts of the couplers which leads to premature failure of the coupling.
Furthermore, many couplers on the market today have either a spring loaded or hydraulic locking arrangement which is not visible from the cab of the machine by the operator. As a result, he is not certain that the coupling is fully locked unless he leaves the cab to check which defeats the purpose of the spring loaded or hydraulic lock. On some couplers if the lock were to fail the bucket or attachment would fall off which creates a safety hazard on construction sites.
The design of the coupling apparatus according to the invention provides an advance in the related art by providing a coupling system which has a minimum number of parts, a minimum increase in the operating weight of the bucket or attachment, can be installed with little or no change in the position of the pivot pins from the original positions, a means to prevent the reciprocal movement of the pivot pins and provide a safer operator installed locking mechanism which is installed and removed from the operator's side of the machine. The lock is so mounted that it has to be fully retracted before the coupler will separate.